Bitumen is a petroleum hydrocarbon used as a feedstock in the production of synthetic crude oil. For purposes of the present invention, bitumen is defined as high molecular weight hydrocarbons that are solid at ambient temperatures and mostly soluble in alkanes such as hexane. Bitumen recovered from sources such as tar sands or oilsands generally include a component commonly referred to as asphaltenes. The asphaltene component generally consists of hydrocarbons having a higher molecular weight than the bulk of the bitumen, and includes polynuclear aromatic species and metal porphyrins. By definition, asphaltenes are insoluble in alkanes. The asphaltenes, if present in too high of a concentration in the bitumen, cause a number of problems in downstream processing, from emulsification to fouling to poisoning of catalysts, and degrade the value of the synthetic crude produced.
There have been many efforts in the past to extract bitumen from matrixes that include mineral solids. U.S. Pat. No. 4,640,767 to Zajic, et al., discloses the use of materials of a biological origin in extracting hydrocarbons from minerals deposits. It is disclosed therein that microorganisms can be used to prepare a “separation effecting material” by means of fermentation.
A process for extracting bitumen from oilsands is disclosed in U.S. Pat. No. 6,214,213 B1 to Tipman, et al. In this process, a paraffinic solvent is used to separate the bitumen from undesirable mineral solids. Although this process can be run without precipitating asphaltenes, it is advantageous to remove asphaltenes to facilitate processing at lower temperatures (40-50° C.) and into higher quality crude. When the amount of solvent added is high enough to cause asphaltenes to precipitate, the asphaltene content in the bitumen settles out in the same direction as the water and mineral. This, however, produces an asphaltene and solids residue that cannot be removed from a vessel by conventional means.